Oxide indicator



1963 A. P. KELLEY 3,070,

' OXIDE INDICATOR Filed Aug. 28, 1957 INVENTOR. ARCH/BALD P. KELLE Y,

Jfi mo 5. 4M

A Nor/fey.

United States Patent Ofiice 3,070,994 Patented Jan. 1, 1963 tion ofCalifornia Filed Aug. 28, 1957, Ser. No. 680,837 8 Claims. (til. 7361)This invention pertains to a device for determining the percentage of anoxide of an alkali metal dissolved in a solution of the alkali metal andmore particularly to a device which determines the temperature at whichthe oxide is precipitated from the alkali metal solution.

In all liquid metal systems it is necessary to determine the percentageof oxide of the liquid metal dissolved in the system to prevent unduecorrosion of the materials of the system and to prevent plugging ofrestricted passages of the system.

It is well known that the percentage of an alkali metal oxide soluble ina liquid metal varies directly with the temperature of the liquid metal.mine the temperature at which the oxide is precipitated from thesolution, the percentage of the oxide in the solution can easily bedetermined from a suitable graph or other data.

This invention provides a device for determining the temperature atwhich the oxide is precipitated from the liquid metal utilizing aby-pass line to by-pass a portion of the liquid metal being circulatedin the system. According to the invention, a plate having a quantity ofsmall openings is mounted transversely in the by-pass line so that theopenings will be plugged by the oxide when it.

is precipitated from the liquid metal. Mounted upstream from the plateis a suitable cooling means for cooling the liquid metal so as toprecipitate the oxide therefrom. Suitable temperature sensing means aremounted on each side of the plate, such as thermocouples, to sense thetemperatures of the liquid metal on each side of the plate. When the twotemperatures vary by more than a set amount, it indicates that theopenings in the plate have been plugged, thus preventing fluid flow pastthe plate. The plugging of the plate, of course, indicates theprecipitation of the oxide from the liquid metal. At this point thetemperature immediately upstream of the plate is observed, whichtemperature corresponds to the temperature at which the oxide isprecipitated from the liquid metal.

Accordingly, it is the principal object or" this invention to provide asimplified method of determining the amount of oxide dissolved in aliquid metal solution utilizing a flat plate having a quantity of smallopenings and temperature sensing means to determine when the openings inthe plate are plugged by the oxide precipitated from the solution.

Another object of this invention is to provide a simplified method fordetermining the amount of oxide in a liquid metal solution, which methodutilizes temperature responsive means to determine when the flow pastthe plate having the small openings ceases and also the temperature ofthe liquid metal solution at the point at which the flow stops.

These and other objects and advantages of this invention will be moreeasily understood by those skilled in the art from the followingdetailed description of a preferred embodiment when taken in conjunctionwith the attached drawing showing a schematic arrangement of a systemconstructed according to this invention for determining the percentageof an oxide dissolved in a liquid metal solution.

The indicating device of this invention is shown installed in a liquidmetal system which includes a sump ank it). A pump 11 is provided forcirculating the liquid Thus, if one can determetal from the sump throughthe remainder of the systern, not shown. The pump suction is connectedto the sump tank by means of a conduit 12 while the pump discharge isconnected to the remainder of the system by means of conduit 13. Aconduit 14 returns the liquid metal to the sump tank so that it may berecirculated by the pump.

A small by-pass line 20 is provided for by-passing a small portion ofthe liquid metal flow from the conduit 13 back to the conduit 14. A flatplate 22 having a plurality of small holes 27 is mounted transversely inan enlarged portion 21 of the by-pass line 2%. The openings in the flatplate 22 are sized so that they will be plugged by the oxide which isprecipitated from the liquid metal solution flowing in the by-pass line.In one particular design of this indicating device it was found that ina oneinch diameter plate, seventeen -inch diameter holes were adequatein a system handling a solution of liquid sodium and potassium. Ofcourse, for other liquid metals a different size or number of holes maybe desirable.

A wrap-around heat exchanger 24 is mounted so as to surround a portionof the by-pass line upstream from the fiat plate 22. The heat exchangeris provided with an inlet opening 25 and an outlet 26 so that a suitablecooling fluid may be passed through the heat exchanger to cool theliquid metal solution. Thermocouple elements 30 and 31 are attached tothe by-pass line on opposite sides of the fiat plate 22 for sensing thetemperature of the liquid metal flowing in the by-pass line on oppositesides of the plate. While thermocouples are shown in the attacheddrawing, other temperature sensing devices, such as thermometers, mayalso be used. The outputs from the two thermocouples 36 and 31 areconnected to the opposite corners of the bridge circuit 32, theunbalance signal of which is connected to an amplifier or relay device33. The amplifier or relay device 33 should be adjusted so that it willtransmit a signal to close a switch 34 when the difference between thetwo temperatures sensed by the thermocouples 30 and 31 exceeds a smallpredetermined amount on the order of five to ten degrees Fahrenheit. Theswitch 34 closes to complete a circuit from the thermocouple 35 to theindicating device 36. The thermocouple 35 is attached to the by-passline adjacent the upstream side of the fiat plate to determine thetemperature of the liquid metal solution at the instant in which adifierence between the temperatures sensed by the thermocouples 3i and31 exceeds the small predetermined value.

In order to operate the above-described indicating device, one firstmust establish a flow of liquid metal through the bypass line 20. Whenthere is a continuous flow through the by-pass line 20, the twothermocouples 30 and 31 will indicate substantially the sametemperatures. Thus, the relay device 33 will not close and notemperature will be recorded on the device 36 from the thermocouple 35.Next, a cooling fluid is circulated through the heat exchanger 24 tolower the temperature of the liquid metal below the temperature of theliquid metal being circulated in the main system. As the temperature ofthe liquid metal is lowered, a temperature will be reached at which theoxide is precipitated from the liquid metal. The temperature at whichthe oxide is precipitated, of course, is proportional to the amount ofoxide dissolved in the liquid metal. The point at which the oxide isprecipitated from the solution is determined by the difference etweenthe temperatures sensed by the thermocouples 30 and 31. As pointed outabove, these temperatures will be substantially equal as long as thereis a flow through the openings 27 and the plate 22 but will differ by asubstantial amount when the flow is stopped by oxide plugging theopenings 27 in the plate 22.

When the flow past the plate is stopped by the precipitated solids ofthe oxide plugging the openings the temperatures on opposite sides ofthe plate will differ, with the downstream temperature exceeding theupstream temperature. This results from the fact that the heat transferthrough the plugged plate is poor, compared with the transfer when flowexists. Thus, the hotter liquid metal flowing in the return conduit 14will increase the temperature on the downstream side of the plate whilethe upstream side remains cool.

The relay device 33 can be set so that when this difference intemperature is reached it will close the switch 34- so as to indicatethe temperature of the liquid metal upstream of the plate 22. at thisinstant. From this temperature one can easily determine the amount ofoxide in the liquid metal.

After the desired oxide reading has been taken, the openings in theplate 22 can be unplugged by stopping the flow of cooling fluid to theheat exchanger 24. This will increase the temperature of the liquidmetal in the by-pass line 20 in order to redissolve the oxide in theliquid metal solution. If desired, the oxide content of the liquid metalcan be determined by observing the temperature at which the oxideredissolves in the liquid metal instead of using the temperature atwhich it precipitates from the liquid metal.

While the above invention was described as using three thermocouples todetermine the stoppage of flow through the plate 22 and the temperatureat which the flow was actually stopped, these conditions could also bedetermined by using only two thermocouples and visually observing thedifference between the two thermocouple readings. When the differencebetween the two readings exceeds a small value on the order of five toten degrees Fahrenheit, one can visually observe the temperatureindicated by the thermocouple 30 mounted upstream from the plate 22.This temperature, of course, is the temperature at which the oxide isprecipitated from the solution. In cases where it is only necessary toknow the temperature at which the system would plug due to oxide beingprecipitated from the system, it would be unnecessary, of course, toconvert this temperature to an oxide reading.

This invention thus provides a simple means using only temperaturesensing elements to determine both when the flow past the plate 22. isstopped by the precipitated oxide plugging up the openings in the plate,as well as to indicate the temperature at which this plugging occurs.Temperature sensing devices such as thermocouples are very rugged andrelatively simple to build and maintain, thus eliminating a major sourceof trouble with previous indicating devices which depended upon othermeans for determining when the flow past the plate 22 stopped.

While but one preferred embodiment of this invention has been describedin detail, many modifications and improvements will occur to thoseskilled in the art within its broad spirit and scope.

I claim:

1. In a method of determining the amount of an oxide of an alkali metaldissolved in a solution of the metal, the steps comprising: passing aliquid solution of the metal through a passage means containing a flowrestriction; cooling said liquid solution upstream of said flowrestriction; measuring the temperatures of said solution on each side ofsaid flow restriction; and recording the temperature of said solutionupstream of said flow restriction at the instant the temperatures onopposite sides of said flow restriction differ by more than apredetermined amount.

2. A device for determining the amount of an oxide of an alkali metaldissolved in a solution of the metal comprising: a conduit; a platemember mounted transversely in said conduit, said plate having aplurality of small openings; means for establishing a flow or" a liquidsolution of the metal and oxide through the conduit; temperatureresponsive means disposed to sense the temperature of said solution onopposite sides of said plate; a heat exchanger disposed adjacent saidconduit upstream of said plate to cool said solution; means for sensingthe difierence between the temperatures of the solution on oppositesides of said plate; and indicating means rendered operative when apredetermined difference between such temperatures is exceeded,

3. A method for determining the amount of an oxide of an alkali metaldissolved in a liquid solution of the metal comprising the followingsteps: establishing a flow of a liquid solution of the metal through aconduit containing a flow restricting means; cooling the solutionupstream of said flow restricting means; measuring the temperature ofthe solution on opposite sides of said flow restricting means; measuringthe temperature of the solution upstream of said flow restriction whenthe temperatures on opposite sides of said flow restriction vary by apredetermined amount; and comparing the temperature of the solutionupstream of said flow restriction with previously established data todetermine the amount of oxide in the solution when the temperatures atthe upstream and downstream sides of the how restricting means vary by apredetermined amount.

4. In a method for determining the amount of an oxide of an alkali metaldissolved in a solution of the metal, the steps comprising: establishinga how of a liquid solution of the metal and oxide through a conduithaving a flow restricting means; stopping said flow by cooling thesolution to precipitate the oxide from the solution to plug said flowrestricting means; sensing the temperature difference across said flowrestricting means to determine the stopping of said flow; and comparingthe temperature of the solution when said flow is stopped with knownstandard data to determine the amount of oxide present in the solution.

5. In a method of determining the amount of an oxide of an alkali metaldissolved in a solution of the metal, the steps comprising: establishinga fiow of the solution through a conduit containing a flow restrictingmeans; cooling the solution upstream of said flow restricting meansuntil the oxide is precipitated from the solution; and detecting thethermal point at which the oxide is precipitated by sensing thetemperatures on opposite sides of the flow restricting means.

6. In a liquid metal system of the type having a sump, a pump, apressure conduit leading to said pump and thence to the system, and areturn conduit leading from the system to said sump, an oxide indicatorcomprising: a by-pass conduit extending from the pressure conduit at theoutlet side of the pump to the return conduit; means forming a chamberin said by-pass conduit; wall means extending across said chamber, saidwall means having a plurality of restricted openings extendingtherethrough; means between said pressure conduit and said chamberforming means for reducing the temperature of fluid flowing to saidchamber; temperature sensing means supported by said bypass conduit ateach side of said wall means; and temperature indicating meansoperatively connected with said by-pass conduit at one side of saidwall, said temperature indicating means being connected in circuit withsaid temperature sensing means and responsive to a predeterminedtemperature dififerential between the liquid metal at opposite sides ofsaid wall means to indicate the temperature of the liquid metal at oneside thereof.

7. In a liquid metal system of the type having a sump, a pump, apressure conduit leading to said pump and thence to the system, and areturn conduit leading from the system to said sump, an oxide indicatorcomprising: a by-pass conduit extending from the pressure conduit at theoutlet side of the pump to the return conduit; means forming a chamberin said bypass conduit; wall means extending across said chamber, saidWall means having a plurality of restricted openings extendingtherethrough; means between said pressure conduit and said chamberforming means for reducing the temperature of flui flowing to saidchamber; temperature sensing means supported by said bypass conduit ateach side of said wall means; a second temperature sensing meanssupported by said by-pass conduit at one side of said wall means; anindicator; and an electrical circuit including a Wheatstone bridgeconnected with the first-mentioned temperature sensing means; a relaydevice connected for control by said Wheatstone bridge; and a switchelectrically connected between the second temperature sensing means andsaid indicator, said switch being connected for control by said relaydevice.

8. In a liquid metal system of the type having a sump, a pump, apressure conduit leading to said pump and thence to the system, and areturn conduit leading from the system to said sump, an oxide indicatorcomprising: a by-pass conduit extending from the pressure conduit at theoutlet side of the pump to the return conduit; wall means extendingacross said by-pass conduit, sa-id wall means having a restrictedopening extending therethrough; means adjacent said pressure conduit forreducing the temperature of fluid flowing to said restricted opening;temperature sensing means supported by said by-pass conduit at each sideof said wall means; additional temperature sensing means operativelydisposed adjacent said bypass conduit at one side of said wall; anindicating device in circuit with said additional temperature sensingmeans; and switch means between said indicating device and saidadditional temperature sensing means, said switch means being operativeto connect said additional sensing means and said indicating device inresponse to a predetermined differential in temperatures sensed atopposite sides of said wall means.

References Cited in the file of this patent Liquid Metals Handbook,Atomic Energy Commission, 3rd edition, Jun 1955, pp. 103-4, Fig. II28.(Copy available in Scientific Library of U.S. Patent Ofiice.)

1. IN A METHOD OF DETERMINING THE AMOUNT OF AN OXIDE OF AN ALKALI METALDISSOLVED IN A SOLUTION OF THE METAL, THE STEPS COMPRISING: PASSING ALIQUID SOLUTION OF THE METAL THROUGH A PASSAGE MEANS CONTAINING A FLOWRESTRICTION; COOLING SAID LIQUID SOLUTION UPSTREAM OF SAID FLOWRESTRICTION; MEASURING THE TEMPERATURES OF SAID SOLUTION ON EACH SIDE OFSAID FLOW RESTRICTION; AND RECORDING THE TEMPERATURE OF SAID SOLUTIONUPSTREAM OF SAID FLOW RESTRICTION AT THE INSTANT THE TEMPERATURES ONOPPOSITE SIDES OF SAID FLOW RESTRICTION DIFFER BY MORE THAN APREDETERMINED AMOUNT.